With the ballast water, ships take up the most heterogeneous animal and vegetal organisms, e.g. mussels, fish, worms, crabs, bacteria, viruses and so on, which they set free again in extraneous regions where these are not native. These organisms often can spread rapidly in their new environment, because natural enemies are lacking. Through this, big ecological and/or economical damages can be brought about.
Different methods to prevent release of organisms with the water in tanks are known, e.g. by filtration, heat treatment, by reverse osmosis or UV-irradiation. Further, it is known to chemically combat organisms in water. All the stated methods are insufficient when applied to ballast water, however. The ballast water is conveyed into the ballast tanks in a very short time with a very high speed or high volume, respectively. In doing so, it must be ensured that the ballast water has been made aseptic to a large extent in this relatively short period of time.
The invention has the objective to create an installation for the removal and the deactivation of animal or vegetal organisms in the ballast water, which fullfills the security standards upon filling or clearance of the tanks with sparsely sumptuous means. Further, the installation according to the invention should bring about little expenditure in apparatus and should also be susceptible to be backfitted in a simple manner, e.g. on ships.
The installation according to the invention consists of at least two components. One of them has a gravity precipitation, e.g. a group of hydrocyclones which are parallel connected, a control equipment providing that only as much hydrocylones are in operation as is needed. As is generally known, hydrocyclones have only a restricted range of operation. That is why a control equipment switches the hydrocyclones on or off, in accordance with the conveying volume. The hydrocyclones do not only significantly reduce the sediment load carried along with the water, but they also remove a great deal of bigger organisms, in a dimension of more than 300 μm, e.g. The hydrocyclones are dimensioned such that these organisms can be efficiently separated, even when their specific weight is only faintly larger than 1.
A peculiarity of the hydrocyclones is that an arbitrary number can be connected together, in order to adjust them to any arbitrary quantity passing through, within the framework of their operating optimum. Hydrocyclones have also the advantage that they are almost maintenance-free and operationally reliable. They are insensitive against occlusions and can be simply and quickly attended, as the case may be. According to one form of the invention, they have a wear-resisting, corrosion-proof surface, e.g. in the form of a coating. Through this, the inner walls are protected against abrasive and corrosive strains.
The first feed pump is preferably a rotatory pump, as is usually in operation as a ballast water pump, e.g.